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Finding the Fourth Proportional to 1,221.94, 1,687 and 780.22

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Solution

The fourth proportional to 1,221.94, 1,687 and 780.22 is: 1,077.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.94 : 1,687 = 780.22 : x
  2. Step 2: Convert to fraction form
    1,221.94/1,687 = 780.22/x
  3. Step 3: Cross multiply
    1,221.94x = 1,687 × 780.22
  4. Step 4: Simplify right side
    1,221.94x = 1,316,231.14
  5. Step 5: Solve for x
    x = 1,316,231.14/1,221.94
  6. Step 6: Final answer
    x = 1,077.17

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.